King's Highway 427 is an urban freeway which forms an important north-south highway link through the City of Toronto. The highway
primarily serves as a commuter route, connecting the Queen Elizabeth Way (QEW) and the Gardiner Expressway to Highway 401 and Highway 407. The highway was created out
of a route renumbering in 1972, when the existing freeway section of Highway 27 through Etobicoke between
the QEW and Highway 401 was re-designated as Highway 427. In the early 1970s, Highway 427 was linked to Toronto International Airport through an extensive
reconstruction of the Highway 401 and Highway 427 Interchange. Following reconstruction, the route of Highway 427 connected to the Airport Expressway, which was a
short controlled-access highway that had been completed between Highway 401 and Dixon Road in 1963.

The decision to change the route number from Highway 27 to Highway 427 apparently came about in 1968. During the year, surveys and other Department of Highways'
documents began to refer to the freeway section of Highway 27 as Highway 427. The change in route numbers was necessary, since a proposed extension of the freeway
north from Highway 401 to Highway 7 would have ultimately created two routes known as Highway 27 - which would have proved confusing for motorists. Early surveys done
for the north portion of Highway 427 prior to mid-1968 refer to the route as "Highway 27 New". The original guide sign layouts for the QEW and Highway 427 Interchange
in Etobicoke were initially designed in the 1960s to show the new Highway 427 route number. However, a decision was made to not introduce the new route number until
reconstruction of the existing Highway 27 wrapped up. The signs along Highway 27 were changed over to Highway 427 at the conclusion of construction in 1972.
Introduction of the Highway 427 route number on the section of the highway north of Highway 401 was also deferred, and thus, the route continued to be signed as the
Airport Expressway for many years. Even as late as 1980, all guide signs along Highway 401 for the north leg of Highway 427 still referenced the route as the Airport
Expressway. It is believed that the final Airport Expressway guide sign was removed during reconstruction of the highway between Highway 401 and Dixon Road in 1981.

In 1976, the first in a series of construction contracts was called for the north extension of Highway 427 from Toronto International Airport up to Finch Avenue. This
work included a new interchange at Highway 409. The extension involved upgrading a local collector road known as Indian Line to a freeway. The highway was gradually
extended northwards throughout the late 1970s and early 1980s. Reconstruction of Indian Line continued up until 1983, when all lanes of Highway 427 were opened to
traffic through to Finch Avenue. North of Finch Avenue, Highway 427 narrowed down to two lanes and continued north to Highway 50 (Albion Road) as Indian Line. After
several years' hiatus, the final section of Highway 427 was completed from Highway 50 to Highway 7 near Woodbridge in 1991. The Highway 427 Extension to Highway 7 was
carried out in conjunction with the construction of a new interchange at the proposed Highway 407. In addition, two at-grade intersections along Highway 427 at
Morning Star Drive and the southbound Highway 427 ramp to eastbound Highway 409 were closed off during the 1990s. The at-grade signalized intersection at the
Highway 409 on-ramp was closed permanently in 1992. It was replaced by the current southbound-to-eastbound flyover. The traffic signals at Highway 427 and Morning
Star Drive remained in service right up until 1996, when the at-grade intersection was finally closed off. The grade separation carrying Morning Star Drive over
Highway 427 was built in 2001.

In 2014, construction got underway on a major widening project along Highway 427 between Dixon Road and Finch Avenue. This expansion project will ultimately result in
the implementation of two High-Occupancy Vehicle (HOV) Carpool Lanes (one lane in each direction) on Highway 427 from just south of the Highway 409 Interchange
northerly to Finch Avenue. One additional northbound General Purpose Lane (GPL) was constructed along Highway 427 from Rexdale Boulevard to Highway 407 ETR, in
order to correct a lane imbalance which previously existed on the highway. The Highway 427 widening project from Dixon Road to Finch Avenue was completed in 2018. The
southbound HOV Carpool Lane was opened to traffic from Rexdale Boulevard southerly to Highway 409, but the northbound HOV Carpool Lane will remain closed to traffic
until a follow-up widening project along Highway 427 north of Finch Avenue in completed. This second project will see the HOV lanes extended northerly from the Finch
Avenue area to Highway 7. This work is expected to be complete by 2020, providing that planning, design and funding remain on schedule.

The Ministry of Transportation (MTO) is also extending Highway 427 north from its current northern terminus at Highway 7 towards the Bolton area. The Ontario
Government's Growth Plan for the Greater Golden Horseshoe has identified the need for a new east-west transportation corridor from the Milton area to Vaughan, passing
just to the north of Brampton. The exact route for this future east-west transportation corridor has not yet been finalized. However, it is certain that Highway 427
will be extended to meet this new east-west corridor once a final route has been selected, as the Highway 427 Extension is identified as a necessary highway expansion
in the Growth Plan. The new Highway 427 Extension will add approximately 10 km to the highway's length. Requests for Proposals for the construction of the new
Highway 427 Extension were called in 2017. Construction of the first 6.6 km section of the Highway 427 Extension from Highway 7 to Major Mackenzie Drive began in
2018 and is expected to be completed by 2020. No construction schedule has been established for the remainder of the Highway 427 Extension, as this work depends on
the outcome of the GTA West Route Planning Study.

Highway 427 varies in width from 12 to 14 through lanes (six to seven lanes per direction) from the QEW to Highway 401. This section of Highway 427 features an
Express-Collector Lane configuration. Most sections of Highway 427 north of Highway 401 are six through lanes, but a short section near Pearson Airport has ten lanes.
The highway's cross section is also reduced to four through lanes through several major interchanges. Due to Highway 427's short length, there are no Service Centres
located along the highway. However, services are readily available at all interchanges. Unless posted otherwise, the speed limit on Highway 427 is 100 km/h (60 mph).
Exits along Highway 427 are not numbered, but distances along the highway can be calculated by visiting the
Highway 427 Mileage Chart page.